Single-layer graphene based resistive humidity sensor enhanced by graphene quantum dots

Graphene is broadly applied as sensitive sensing material results from its superb features. Concurrently, as a derivative of graphene with 0D structure, graphene quantum dots (GQDs) offer more possibilities as a supportive sensing material due to its adjustable size and functional group modification. In this work, GQDs are introduced to single-layer graphene (SLG) based humidity sensor to enhance the sensing performance. Specifically, consistent resistance response to relative humidity (RH) is extended from the range of 10%-60% to 10%-90% by contrary to original SLG based sensor. Parallelly, effect of the amount of GQDs is investigated by means of multiple GQDs deposition. As the resultant higher binding efficiency between water molecules and the functional groups of GQDs, improved response rate is observed. For the case of 4-time deposition of GQDs, the response rate (ΔR/R) reaches ∼130% in RH range of 10%-90%. Besides, the response time and recovery time are ∼0.7 s and ∼1.1 s, respectively. The fluctuation of the resistance change of the sensor under constant humidity is less than 5% over a month which demonstrates long-term reliability.